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I've come into possession of a bunch of xenon flasher units of the type commonly mounted to burglar alarms and electric gates. I'm aiming to turn them into tiny strobes as part of a project I'm working on; this means increasing their flash rate from their current rate of ~1 flash per second to several flashes per second.

I've sketched out a rough schematic of what I think is going on inside the unit:

flasher schematic

From what I understand, as C4 charges, the voltage across sidac Q2 increases to the point at which it opens and allows current to flow to T2, which produces the very high ignition voltage that ionises the gas in the tube and causes C2 to dump its stored energy through the bulb, producing the flash.

I have tried lowering the value of R3 and have found that I can get the flash rate a little faster, but once I get below 800kR it makes no difference. Lowering C4 makes a little difference, but below 47nF the bulb won't flash.

It seems that C2 takes around 0.5s to charge (I can hear it), and possibly this is limiting the number of times I can flash the bulb per second. I am drawing around 0.2A from a 12V bench supply capable of providing 2.5A, so there is more power available to play with.

Interested to know peoples thoughts on how to make it flash faster, and I welcome any corrections to my understanding of how things work - my electronics knowledge is flaky at best. Thanks, Tim.

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  • \$\begingroup\$ The easiest way would be to throw everything away and start from scratch. About all components will not be designed to handle the amount of current and heat dissipation needed for strobe light speeds. \$\endgroup\$ – PlasmaHH Jan 31 '18 at 14:32
  • \$\begingroup\$ You could reduce the value of C2 to some extent, it would charge quicker but each flash would be less powerful. \$\endgroup\$ – Finbarr Jan 31 '18 at 14:36
  • \$\begingroup\$ Flash bulbs also have a maximum energy rating. If you exceed that they might explode. Yep found one: youtube.com/watch?v=ZWh7YcO94cA \$\endgroup\$ – Oldfart Jan 31 '18 at 14:45
  • \$\begingroup\$ Thanks all. I suspected that I might have reached the limit of what's possible with that circuit without upgrading every single component. I'm not keen on reducing the brightness too much, so I think I'll leave C2 as it is - the bulbs are wimpy enough already. Thanks for the tip on the exploding bulbs - I have a few spare so I might blow one up at some point when I next get bored ;) It sounds like my little burglar alarm flashers will never be strobes. I think the best I can hope for is to make all seven of them flash at slightly different rates to give a combined effect that is "strobe-like". \$\endgroup\$ – Shedworth Jan 31 '18 at 17:27
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Compare yours with these specs for Joules [Ws] using ½CV² x f rate to determine max flash rate for size of Cap. Reduce C or V value as required.

It seems your charge Voltage may be the limiting factor when rate is increased and that is limited by everything. R1,R2, Q1, transformer...

Don't expect any mobile phone calls when it's running.

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  • \$\begingroup\$ Thanks for the info. You and others have convinced me that no matter how hard they try, these flashers are never going to be strobes. \$\endgroup\$ – Shedworth Jan 31 '18 at 17:30
  • \$\begingroup\$ not true, you just reduce CV² and increase f \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jan 31 '18 at 21:05

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